Brush shunt protector



Feb. 13, 1951 E. MARTIN 2,541,527

BRUSH SHUNT PROTECTOR Filed NOV. 3, 194'?r Patented Feb. 13, 1951 UNITED STATES PATENT OFFICE BRUSH SHUNT PROTECTGR Erle Martin, West Hartford, Conn., assigner to United Aircraft Corporation, East .Hartford Conn., a corporation of Delaware Application November 3, 1947, Serial No. 783,654

6 Claims. l

This application relates to brushes for conducting electricity be ween relatively rotating elements, and particularly to the shunt connecting the brush with a contact member.

An object of `this invention is an electrical brush of an improved and more durable construction.

A further object is to prolong the life of the brush shunt.

A still further object of this invention is a protected brush shunt.

Other objects and advantages will be apparent from the specification and claims, and from the accompanying drawings which illustrate what is now considered to be a preferred embodiment of the invention.

Fig. l is a side elevation, with portions in section, of a multiple brush holder.

Fig. 2 is a detailed enlarged elevation, with portions in section, showing the details of the improved brush construction.

The brush forming the subject of this application may have many uses but nds particular utility in transmitting electricity from the nose of the engine to the hub of an aeronautical propeller, r the purpose ol conducting electricity to the blade heating means. electricity is used to heat selected portions of the blade to prevent the formation of ice thereon or to remove ice that may have formed. Aeronautical propellers are subject to severe vibration and it has been found in practice that the flexible shunt connecting the brush with the contact member failed after a very short period, such as ten hours of running, this failure taking place most frequently near either the brush itseli1 or the Contact member where the shunt was supported and restrained and hence, somewhat less flexible than in the intermediate portion.

Applicant has found that by supporting the shunt within a casing of sponge rubber he is able to prolong the life of the shunt to several hundred hours instead of the ten hours mentioned above, In the embodiment shown, the brush member i5, which may be of carbon or any other suitable material, rigidly supports the shunt I2, by means conventional to the brush manufacturing art, thus giving one end of the shunt a firm support in the brush iii. Shunt I2 maycomprise a plurality oi' small wires of copper or other suitable material twisted, braided or woven into a flexible assembly. The opposite end of the shunt may pass through and be supported in, a contact member ill which may be of silver plated copper or any other suitable material. The shunt I2 may be soldered in position in contact member I4 after being splayed out in countersunli portion I6 of contact member tri. A compression spring I8 extends between brush it and contact member i4 andl tends to 1seep shunt I2 under tension. The spring it is guided on brush it by a pilot 2] and on cap it by a pilot 22.

A sponge rubber casing indicated generally at 23 surrounds shunt i2 and ills the space between tlie shunt and spring i8, thus supporting the shunt in a central position within the spring. The sponge rubber may be of two densities to better support the shunt. Rubber of a heavy density may be placed close to the contact member, as at 25, and close to the brush, as at 28, to help support the restrained portions of the shunt. The sponge rubber 2li between these two dense portions may be of a less dense and more flexible nature to permit flexing of the shunt when the spring and rubber are compressed as when the brush is in operating position.

Brush it may be hexagonal in shape to fit a hexagonal brush holder but the contact member may be cylindrical.

hole.

In order to support the brushes in operative position, a brush holder, indicated generally at 3d, is supported on a frame 32 which may be removably secured to the engine nose. Bolts 34 pass through a block of insulating material 36 forming a portion of the brush holder 30 and through' frame 3?. to secure the brush holder in position on frame member 32. A bus bar 38 is secured in position on the insulating material 36 and at one end carries means for connecting the bus bar with a source or" electricity, indicated in the drawings as a Wire All.

Insulating material 35 supports a plurality of brush holders comprising hollow cylindrical sleeves 2 radiating from a common center concentric with slip ring is mounted on the inboard end of a propeller hub and rotatable therewith. Hollow sleeves i2 may be hexagonal on the interior so as to fit and guide brush It. The brush assembly shown in Fig. 2 is inserted through the open end of the sleeve i2 so that cylindrical Contact member l slides within the hexagonal A. rubber ring member it is received in a groove in contact member i4 and provides sumcient friction between contact member I4 and sleeve 32 to retain the brush assembly in the sleeve i2 aiter the brush is assembled with the sleeve.

It is apparent that insertion of the brush assembly into the hollow sleeve Will force the contact member lli into contact with the bus bar 38 and Will compress spring I8, and sponge rubber 24. This compressed spring and rubber act to urge contact member Ill into contact with bus bar 38 and to urge brush iti outwardly into contact with slip ring 44.

In the manufacture of the brush assembly shown in Fig. 2, shunt l2 is permanently attached to brush it and spring I8 is then assembled over shunt I2. The opposite end of shunt i2 is passed through, and soldered onto, cap i4. Uncured sponge rubber is out in strips and. wrapped around shunt l2 between the coils or spring I8. Ribbons of dense rubber having a blow ratio of about 1:21/4 being used at the opposite ends of the shunt and less dense rubber having a blow ratio of about 1:5 being used in the intermediate portion. A mold tting the outside of the spring convolutions is placed around the above described assembly and the entire assembly is subjected to heat. The rubber has been impregnated so that the heat will cause it to expand, or blow, substantially filling the mold and torming the sponge rubber. IThis mold may then be removed and the brush is ready for use. The heat vulcanises the sponge rubber into a single complete sleeve, vuloanizing the parts of diierent densities together. There is some tendency to Vulcanize the rubber sleeve to the shunt and the contact member but such vulcanization is not essential.

The completed spring and sponge rubber assembly should have a diameter .sufficiently small so that the compression incident to assembly will not enlage it sufliciently to bind in the brush holder sleeve 42.

The rubber casing acts to prevent the brush shunt from bending sideways suihciently to chate on the springs and also prevents the shunt from vibrating and causing :fatigue failures, particularly near the restrained end portions oi" the shunt.

In addition, the rubber acts as a 'form of damper which will prevent the brush from chattering due to the vibration.

It is to be understood that invention is not limited to the speciiic embodiment herein illustrated and described, but may be used in other ways without departure from its spirit as deiiried by the following claims.

I claim:

1. In combination with a brush, a contact member, a flexible shunt connected at one e` d with said brush and at the other end. with said contact member, and a compre sion spring between said brush and contact member and surrounding said shunt; a sponge rubber c sing surrounding said shunt and substantially filling the space between said shunt and said spring and extending from said brush to said contact member.

2. In combination with a brush, a contact member, a brush shunt, connected at one end with said brush and at the other end with said contact member, and a compression spring between said brush and Contact member and sur-- rounding said shunt; a cellular rubbere casing surrounding said shunt and substantially filling the space between said shunt and said spring and extending between said brush and said Contact member.

3. In combination with a brush, a contact 4 i member, a flexible shunt secured at one end to said brush and at the other end to said cont( et member, said flexible member being restrained adjacent said brush and said contact member by attachment thereto, and a compression spring surrounding said shunt; means for protecting said shunt from damaging vibrations compri ing a relatively dense sponge rubber casing surrounding the restrained portion or said shunt and substantially filling the space between shunt and said spring and a relatively less dense sponge rubber casing surrounding Caid shunt and extending between and vulcan d to said relatively dense casings and` substantially nlling the space between said shunt and said spring.

4.. In combination with a brush, adapted to fit and slide within a brush holder, a contact member adapted to slide within said crush holder, and a flexible shunt secured at one end to said brush and at the other end to said contact member; means for protecting said shunt from damaging vibrations comprising a sponge rubber casing surrounding said shunt and extending between said brush and said contact member and having an outside diameter smaller than, but substantially as large as the brush or the contact member so as to slide within but not bind in said brush holder.

5. In combination with a brush, adapted to rit and slide within a brush holder, a contact member adapted to slide within said brush holder, and a flexible shunt secured at one end to said brush and at the other end to said ccntact member, said flexible member being restrained adjacent said brush and said contact einher by its attachment thereto; comprising a relatively dense sponge rubber casing surrounding the restrained portion of said shunt and a relatively less dense sponge rubber casing surrounding said shunt and extending between and vulcanized to said relatively dense having an outside diameter smaller than but substantially as large as the brush or the contact member so as to slide within but not bind in said brush holder.

In combination with a brush, a contact member, a ilexible shunt connecting said brush and said contact member and a compression spring surrounding said shunt and extending between said brush and contact member; shunt supporting means comprising a non-metallic resilient tube encasing and supporting said shunt and substantially filling the spa-ce between said shunt and said spring and extending between said brush and said contact member.

ERLE MARTIN.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 1,733,866 Crossley Oct. 29, 1929 '1,936,389 Hallquist ov. 2l, i933 2,303,515 Toepfer Dec. l, 3.942 2,428,250 Thomas Sept. 3G, 1947 2,434,740 Glaser et al Jan. 2f), 1941.8 

